As used herein GTL-process means a process for production of hydrocarbons requiring a H2/CO molar ratio of 2.3 or below, such as a process for production of diesel via Fischer-Tropsch synthesis in which synthesis gas is converted into liquid hydrocarbons via Fischer-Tropsch reactions, or equivalent process such as a process for production of gasoline in which synthesis gas is first converted to oxygenated compounds in the form of methanol and dimethyl ether (DME) and subsequently to gasoline as disclosed in patents U.S. Pat. No. 4,520,216 and U.S. Pat. No. 4,481,305.
EP-A-0287238 discloses a process under normal operation for the production of hot pressurised hydrogen-containing stream in which a recycle portion of the hot product gas stream from a catalytic partial oxidation reactor is combined with the gas feed in order to preheat the gas fed to the combustion catalyst, thereby enabling easier catalytic combustion. The recycle gas contains not only hydrogen, but also steam.
EP-A-1400489 discloses also a process under normal operation for the production of synthesis gas in which a portion of the effluent from an autothermal reformer is recycled into the hydrocarbon-steam mixture entering the autothermal reformer by means of a thermo-compressor ejector which uses said mixture as motive fluid. The recycle contains not only hydrogen, but also steam to enable soot-free operation of the autothermal reformer and thereby avoid plugging of the catalyst bed.
It is also known to recycle under normal operation a portion of the effluent stream in the form of CO2 from an autothermal reformer into the natural gas fed to the autothermal reformer. The effluent stream from the autothermal reformer is dehydrated first and then passed through a CO2-removal unit in order to form a synthesis gas stream and a CO2-stream. The CO2-stream is recycled and mixed with the natural gas upstream the autothermal reformer.